@Gina *******
the cost to extend here is 1900THB, you get 30 days and it's really easy. There is no 15 day one. Just go to the immigration office by where you are staying, sorry no idea about Kamala beach Every immigration office has different requirements so you'd need to check the local one to see what you need.
If you want the single entry tourist visa, 60 day stamp you apply using the evisa system and no longer have to mail your passport. Manitoba west, select the consulate in Vancouver. If in the east use the embassy in Ottawa. No idea how long it takes but I think the embassy shows 5-7 business days(?).