Hoeveel aanbetaling is normaal bij het huren van een condo voor de langere termijn in Phuket?

A two-month deposit plus the first month up front is the most common arrangement for a long lease. Take dated photos of the condition at move-in, get the inventory in writing, and check who pays for what (water and internet are often included, electricity almost never is and is billed per unit). Read the terms on getting the deposit back before you sign.