@Sri **
Moreover, each border has their own rules. The most generous are the Burmese borders. Off the top of my head, here are the rules for Thais using border passes:
Myanmar borders:
Mae Sot: 1 day with car permitted within 12km of the border to Myawaddy. 7 days without vehicle and permitted to stay overnight in Myawaddy. Must use local transportation as Thai cars are not allowed to remain overnight in Myawaddy.
Mae Sai: 7 days with car permitted but only in Tachilek. Beyond that, a passport is required with a 14 day pass that allows travel up to Kengtung or sometimes even Mong Lar. Must return the same way you came. Else, a passport + Myanmar visa or e-visa and then you can travel to other parts of the country and exit from a different border. Permitted length of stay for tourist visa holders: 28 days. Must fly from Tachilek or Kengtung if seeking to travel to the "interior" of Myanmar. Overland travel west of Kengtung requires special permission and can't be granted on the spot.
Phu Nam Ron, Kanchanaburi: Thais can get a 7-day pass to travel to Dawei and back. Permission is granted to stay overnight at beaches just to the north and south of Dawei, down to Grandfather beach. If seeking to travel south to Myeik or north to Mawlamyine, a passport with visa is required. Thais using a border pass will be arrested. There is a checkpoint about 100km north of Dawei and hotels outside of Dawei and nearby beaches won't accept a Thai border pass. Thais registered in Kanchanaburi can get a 14-day border pass and have the same restrictions on travel.
Dan Singkorn, Prachuab Khiri Khan: Thais on a border pass can get a 14-day pass to travel to Myeik and its immediate surroundings. They must return the same way they came. It's illegal to travel north to Dawei or south to Kawthoung on a border pass.
Three Pagodas Pass, Kanchanaburi: a one day pass is issued to Thais with permission to travel no further than the waterfall, about 12km from town.
Ranong pier: Thais receive a 14-day permission to visit the islands of the south and Kawthoung. Generally, they want a passport here but I understand a Thai border pass is equally acceptable. Permission is granted to travel as far as 24km north of Kawthoung.