The newly-minted world number 40 is seeded eighth for the tournament, and more than justified that billing as she raced into a 6-1 3-0 lead before her opponent Timea Babos retired from the match.
The Hungarian, ranked 79th in the world, was broken four times before quitting after 54 minutes on court.
Watson reached the third round of the Australian Open before losing to world number four Agnieszka Radwanska in straight sets.
Next up for Watson is Anastasija Sevastova of Latvia, the world number 183 made it into the second round with a 6-4 6-2 win over Misaki Doi of Japan.
Second seed Maria Kirilenko encountered stiff resistance from Uzbekistan's world number 148 Akgul Amanmuradova before winning 6-3 7-5. She will now face Thai wildcard Luksika Kumkhum.
Top seed Ana Ivanovic lost the opening set of her match against Ayumi Morita but had fought back to win the second before rain forced a suspension in the early stages of the decider.
Ivanovic and Morita will resume tomorrow on Court 1, while Sabine Lisicki, Daniela Hantuchova and Elena Vesnina, seeded 5, 6 and 7 in Pattaya, will also be in action.
2-Maria Kirilenko (Russia) beat Akgul Amanmuradova (Uzbekistan) 6-3 7-5
4-Sorana Cirstea (Romania) beat Bethanie Mattek-Sands (U.S.) 6-1 6-3
5-Sabine Lisicki (Germany) beat Tatjana Malek (Germany) 6-2 6-3
8-Heather Watson (Britain) beat Timea Babos (Hungary) 6-1 3-0 (Babos retired)
Anastasia Rodionova (Australia) beat Vania King (U.S.) 6-4 6-4
Anastasija Sevastova (Latvia) beat Misaki Doi (Japan) 6-4 6-2
Kimiko Date-Krumm (Japan) beat Chanelle Scheepers (South Africa) 7-5 6-1
Luksika Kumkhum (Thailand) beat Casey Dellacqua (Australia) 6-2 6-2
Nina Bratchikova (Russia) beat Shahar Peer (Israel) 6-3 6-3