Koh Kood, which is known for its unspoilt white-sand beaches and crystal clear waters, was most popular with up to 3,000 heading there for day trips.
Koh Chang, meanwhile, welcomed some 10,000 holidaymakers during the three-day weekend.
Monday has been tagged onto the weekend as compensation for both Visakha Bucha Day and Her Majesty the Queen’s birthday.
Atthapol Klinthap, manager of the Boon Siri pier in Trat’s Muang district, said on Saturday that some 3,000 tourists will have taken boats to Koh Kood over the weekend.
Four companies have been running shuttle boats from Laem Sok pier to Koh Kood, and as of press time, some 1,500 tourists had used the service since Saturday morning.
Meanwhile, travellers began queuing up in their vehicles from 6am on Saturday for ferry services to the diving paradise Koh Chang. The queue at Trat’s Laem Ngob district was about two kilometres long by 10am, with many tourists complaining they had to wait more than two hours before they got to board the ferry.
Trat is about four and a half hours from the capital.