As I booked hotel through Trip.com at Koh Samui for after the sandboxing, I got this email from them in case someone needs more info for the Koh Samui bubble:
Despite the fact that there will be no quarantine requirements, all travelers will continue to be restricted to stay at some accommodations.· For travelers who wish to visit Samui only, no minimum stay is required but they must leave Samui (Thailand) for another country on or before the intended departure date;· For travelers who wish to continue the journey to other Thai destinations, they must stay in Samui for 14 nights and thereafter will be allowed to travel to other parts of Thailand.Samui Extra Plus Hotels (Day 1-7) in Samui onlyFrom Day 1 to 3, you will be allowed to leave your hotel room to a designated area within the hotel only. From Day 4 to 7, you will be allowed to travel to a designated route in Samui or join a tour program within Samui also. SHA+ Hotels (Day 8-14) in Samui, Koh Phangan and Koh Tao
After spending 7 nights at Samui Extra Plus hotel, you will be allowed to travel freely around Koh Samui, Koh Phangan, and Koh Tao but you will have to stay at an accommodation with a SHA+ certificate, which is issued by the Thai government for safety and health measures standards. You will need to stay at SHA Plus hotel for no less than 7 nights and the hotel(s) will need to be pre-booked in advance.
Here are the details of the program. https://www.thaiembassy.com/travel-to-thailand/samui-plus-sandbox-travel-to-thailand-without-quarantine https://www.thaiembassy.sg/sites/default/files/Samui%20Plus%20Eng.jpg