''I'm very happy and proud of my team and the performance we showed. I hope this win gives all the Thai people a boost and encourages them to come to our next match to support us from the stands,'' said the Dutch coach.
''Futsal has a future in Thailand and maybe the fans can become the sixth player on the pitch.''
Thailand suffered three defeats in a five-team warm-up tournament in Bangkok last week and the coach and his players were heavily criticised for their unconvincing performances.
''Many people criticised us last week,'' Hermans said after last night's win. ''Today, we showed we can play like we did in Dubai [where Thailand finished runners-up in the Asian Championship earlier this year].
''Costa Rica squandered several scoring chances but we did too. We deserved to win.''
Thailand will next meet Ukraine in their second Group A match on Sunday. With the Costa Rica win, the Thais are group leaders after Paraguay drew 3-3 with Ukraine.
Suphawut Thueanklang, Keattiyot Chalaemkhet and Jirawat Sornwichian scored for Thailand last night.
The hosts were the better side in the opening minutes with star forward Suphawut tormented Costa Rica's defence.
The Thais took an 18th-minute lead. Predictably, Suphawut was at the heart of the move that led to Keattiyot opening the scoring.
Suphawut went from provider to goalscorer nine minutes into the second half.
Diego Zuniga, who is dubbed 'Ronaldinho of futsal', cut the deficit for Costa Rica before Jirawat Sornwichian restored a two-goal advantage for Thailand.
''We believe that Thailand's No.9 [Suphawut] is a very good player. But we also have to admit that we made too many mistakes in the game, and that cost us the three points,'' said Costa Rica coach Diego Solis.
Paraguay 3 Ukraine 3
Paraguay and Ukraine opened their campaign with a 3-3 draw at Hua Mark Indoor Stadium.
Enmanuel Ayala scored a hat-trick that looked to have secured all three points for Paraguay only to pick up an unnecessary red card that allowed Ukraine to come back.
The 26-year-old's first goal came after nine minutes but Ukraine hit back immediately with Maksym Pavlenko finishing off a slick team move seconds later.
Despite a promising start to the second half, the eastern Europeans conceded a second goal 10 minutes after the restart.
This time, Ayala was fed by a chipped pass from his twin brother, Gabriel, and sent the ball past goalkeeper Ievgen Ivanyak.
Again Ukraine fought back, drawing level from the penalty spot with five minutes remaining, when Petro Shoturma curled in a precise left-footed shot off the inside of the post.
Ayala completed his hat-trick with a coolly-taken penalty of his own just two minutes later, but was then sent off for diving _ his second bookable offence.
Without their star forward, Paraguay were unable to protect the lead with Pavlenko slotting home from an acute angle to secure a deserved share of the spoils.
''I am satisfied with the performance of my players, but not with the result because I think Ukraine should have won,'' said Ukraine coach Gennadiy Lisenchuk.
''But we have drawn against a strong team and that means we are ready to play anyone.''
Paraguay coach Fernando Leite said: ''It was a very tight match, which in the end had a fair result. Neither team played well defensively, and that is something we will have to work on. This result is not a setback and I still believe we can advance to the next round.''