Gonçalves was booked to face Denkongchai Dabransalakham for the vacant
WPMF Lightweight title at the Princess Prathep's birthday event on March 31, 2018. He won the fight by a second-round knockout. Gonçalves participated in the 2018 Muay Xtreme 60 kg tournament, held on June 1, 2018. He faced Christian Hyatt in the tournament finals, after having beat Singthong by decision in the quarterfinals and Sornpetch SamartPayakaroonGym by decision in the semifinals. Gonçalves captured the Muax Xtreme 60 kg title with a first-round knockout of Hyatt. Gonçalves made his first WPMF lightweight title defense against Daraek SutaiMuayThai at the TerdthaiOngracha event on July 26, 2018. He won the fight by decision. Gonçalves faced Chatchai PK.Saenchaimuaythaigym at Top King World Series - TK22 on September 22, 2018. He lost the fight by decision. Gonçalves next faced Pedro Ruiz at Yas Island Muay Thai on November 24, 2018. He won the fight by decision.
ONE Championship Gonçalves faced
Rodtang Jitmuangnon for the
ONE Flyweight Muay Thai World Championship at
ONE: Century on October 13, 2019, in his
ONE Championship debut. He lost the fight by split decision. Gonçalves faced Kohei Kodera at
ONE: Collision Course 2 on December 25, 2020. He lost the fight by a second-round technical knockout, due to a leg injury sustained during the bout.
ONE Flyweight Muay Thai World Grand Prix In the quarterfinal, Gonçalves was scheduled to face
Jonathan Haggerty at
ONE 157 on May 20, 2022. However, Haggerty was forced to pull out of his bout at the last minute due to health issue and was replaced by Josue Cruz. Gonçalves won the fight by a first-round technical knockout. In the semifinal, Gonçalves faced
Superlek Kiatmuu9 at
ONE on Prime Video 1 on August 27, 2022. He lost after getting knocked out with an elbow in the first round.
Post Grand Prix Gonçalves faced Jacob Smith on December 9, 2023, at
ONE Fight Night 17. He lost the fight via knockout in the first round. Goncalves faced Aliff Sor.Dechapan on November 9, 2024, at
ONE 169.{{Cite web |date=2024-10-16 |title=ONE: Walter Gonçalves reforça evento que terá Buchecha e Adriano Moraes ==Mixed martial arts career==