Early career Choo was elected coach of Singapore Chinese F.A. in early 1949. He started coaching
Singapore FA for their
Malaya Cup campaign in March 1949. and as manager and coach of Chinese A.A. a month later. In 1952, Choo became manager and coach of SAFA Second Division Star Soccerites, a club he founded. The club had ended 7th in the league the previous season but finished runners-up in 1952 to secure promotion to the First Division. Star Soccerites won the title in 1954. Choo left Star Soccerites in 1957 and joined Marine Department Sports Club, coaching them to the First Division title. Choo was appointed the first foreign coach of the
Indonesia national team in 1951, which he held in an honorary position concurrent with his club duties. He led the team at the
1951 Asian Games. In April 1953, Indonesia toured Hong Kong, beating professional sides Hong Kong Interport 4–1, Hong Kong Selection 3–2, and Hong Kong Combined Chinese 5–1.
Malaya / Malaysia On 1 February 1958, Choo was employed on $700 monthly wages to coach the
Malaya national team and hold coaching clinics for the Malay states. Choo's first match in charge ended in a 5–2 victory over
Singapore on 2 March. Malaya hosted the five-nation
Merdeka Tournament at the end of August, defeating
1958 Asian Games bronze medalists
Indonesia 3–2 and
Hong Kong 3–0 en route to winning the tournament. Malaya started their defence of the Merdeka Tournament in 1959 with a 4–3 win over
South Vietnam. The team then drew 1–1 with
India before a 2–1 win over Hong Kong confirmed them as champions. Nine countries took part in the 1960 Merdeka Tournament. Malaya began with a 3–0 win over
Japan. An 8–2 defeat of
Thailand and a one-goal win over
Pakistan followed. Malaya shared the trophy with
South Korea after a goalless draw in the final. In January 1961, Choo signed a two-year contract extension with the FAM. Right after extending his contract, Choo departed on a six-month coaching course in England where he was attached to champions
Burnley and other clubs like
Everton,
Sheffield United for the
1960–61 Football League season. The trip was made under a personal arrangement by FAM president
Tunku Abdul Rahman with a
British Council bursary. Choo tendered his resignation as Malayan national coach in 1961 but was persuaded by Tunku to continue in his coaching position. Tunku declared that his resignation "will certainly be a calamity to the football fraternity of Malaya". Malaya scored two late goals in the final ten minutes to defeat hosts Burma 2–0 to win the football competition. Malaya opened their
1962 Asian Games campaign with a 15–1 win over
the Philippines in the preliminary group stage. They finished second in the group and were drawn against
South Korea in the semi-final, which they lost 2–1 after extra time. In the third-place play-off, Malaya defeated
South Vietnam 4–1 to clinch the bronze medal. Choo's contract ended in March 1963 and was not renewed. He was appointed the national schools coach responsible for training and scouting youth players on 1 April. With the delay in the appointment of a new national coach, Choo was tasked by Tunku with coaching the
Malaysia team from 10 September to prepare the players for the
1964 Olympics qualifiers and other upcoming tournaments. Choo left Malaysia at the end of the Merdeka Tournament in September 1964 after he felt he was under-utilised in his coaching capacity. Choo had also rejected coaching offers from Japan, Thailand, Hong Kong and Indonesia during his time with the
FAM.
Singapore The
SAFA had rejected Choo's previous offers to coach the
Singapore national team. The next month, SAFA put in a request to engage Choo's services in training
Singapore FA for the
Malaya Cup.
Tunku Abdul Rahman, the Malaysian Prime Minister and President of the FAM, approved Choo's secondment to SAFA in June. Following a 1–1 draw, Singapore beat
Hong Kong 2–1 in the replay to claim the Aw Hoe Cup, an annual competition between Singapore and Hong Kong, in July. The next month, Singapore defeated
Perak 3–2 in the final to clinch the 1964 Malaya Cup. Choo offered to coach Singapore in January 1965 and SAFA responded with a contract offer of $250 monthly wages plus a cut of the gate receipts in February which Choo accepted in March. Singapore retained the Malaya Cup in 1965, defeating
Selangor 3–1 in the final. For the second consecutive year, Singapore won the Aw Hoe Cup after a replay. In December 1965, Singapore was eliminated at the group stage of the
1965 Southeast Asian Peninsular Games after losses to
Burma and
South Vietnam. On 28 December, the SAFA sacked Choo with immediate effect and dropped six players from national team due to alleged misconduct and insubordination at the
1965 Southeast Asian Peninsular Games. Team manager Tan Peng Yee had reported that Choo "was being difficult from the very moment the team arrived in Kuala Lumpur from Hong Kong". He offered to assist in coaching the national team in June 1966 but was rejected by the
Football Association of Singapore (FAS), formerly known as SAFA, which cited a lack of funds to pay his salary. Choo was one of three coaches appointed to coach the national team reserves in January 1967 and took full reins over the reserves in March. He returned as national coach on 8 August 1967, taking charge of the squad for the Merdeka Tournament in the same month. Singapore ended up last in the 10-team competition. Due to concerns expressed by Sports Minister
Othman Wok that an inter-state competition is inappropriate for the national team, Singapore withdrew from the
Malaysia Cup and
FAM Cup in 1968 and 1969. In his time outside the national team set-up, Choo coached Police Sports Association from September 1968 and led them to the 1968
President's Cup. In June 1971, the
National Sports Promotion Board assigned Choo to the national team coaching panel. Singapore was invited to the 12-nation Merdeka Tournament in August. The team defeated
Hong Kong 2–1 and achieved a shock 1–0 win over pre-tournament favourites and
1970 Asian Games champions
Burma. Singapore failed to make the semi-finals after a 4–4 draw with
the Philippines. Choo later resigned in December due to poor health. In 1973, Choo rejected a coaching contract worth $2,800 per month, with first-class board and lodging, and free transport from professional Hong Kong club Caroline Hill FC. but resigned after two months. The FAS rejected Choo's application for national coach in September 1974. Between 1971 and 1975, Choo was also honorary coach of local clubs including Burnley United, Singapore Marble,
Tampines Rovers, and Farrer Park. On 2 September 1976, Choo was appointed to coach Singapore for the
preliminary World Cup tournament in February 1977 in his 4th stint with the FAS. His appointment prompted FAS advisor
Trevor Hartley, coach Hussein Aljunied and trainer Andrew Yap to resign from the coaching panel although Hussein would return to assist Choo in late September. With the support of newly elected FAS chairman
N. Ganesan, Choo was able to have non-interference in matchday selection of players for the first time. They then defeated fancied
Malaysia 1–0 to secure a play-off spot despite losing to
Indonesia in the last group match. In the play-off match on 12 March, Singapore lost 1–0 to Hong Kong to eliminate their chances of reaching the final qualifying round. Choo had announced his intention to relinquish his position after the play-off due to his advanced age and a need to focus on his business. but eventually stayed on as national coach on a voluntary basis with performance-based payouts. Twelve years after its last triumph, Singapore defeated
Penang 3–2 to win the Malaysia Cup on 28 May. Following reported unhappiness of the players over the disparity in bonuses and mistreatment by the management leading to an alleged boycott of training, Choo rejected a one-year contract offer by the FAS and tendered his resignation on 27 June but withdrew it after talks with the FAS and the national players. Choo had developed a skin infection on his right leg after a fall sustained during the Malaysia Cup semi-final second leg against Selangor in May. He failed to seek treatment and with diabetes as a complication, gangrene set in. He had his lower right leg amputated in September. He returned to coaching with Malaysian outfit
Johor FA midway through the 1980 season but left the team abruptly in January 1981. == Personal life ==