PT Prachuap condemned hosts Rayong to Thai League 2 with a 3-1 win last night.
Brazilian Willen Mota scored a hat-trick for the Killer Wasps who are now eight points above the red zone.
In the other game, Willen's compatriot Dennis Murillo did even better as he netted four times in Nakhon Ratchasima's 4-1 win over visiting Muang Thong United.
Promoted club Rayong will make a quick return to the second tier next season with four games remaining in the top flight this campaign.
The Dragon Horses became the first team to be relegated from Thai League 1 this term.
Willen opened the scoring for Prachuap after just four minutes only for Yordrak Namuangrak to equalise in the 18th minute.
But the visitors proved too strong for Rayong as Willen added two more goals in the 23rd and 61st minutes.
At Nakhon Ratchasima, the hosts had promised not to emulate English Premier League champions Liverpool who have suffered a record six successive losses at home.
There was a billboard outside the stadium which read "This is KORAT [Nakhon Ratchasima] not ANFIELD."
Derley gave the visitors the lead after 23 minutes only for Dennis to score four unanswered goals.
The Brazilian opened his account after 42 minutes and found the back of the net three times in the second half.
Muang Thong's Wattanakorn Sawatlakhorn was sent off for handball in the 77th minute.
