Thailand gives you ancient temples in Chiang Mai, street food in Bangkok, and quiet beaches down south. May through October is the rainy season, which means fewer crowds and much cheaper flights and hotels if you do not mind a daily downpour.
When you are looking at about $2600 for the whole trip, spreading out the cost helps keep your bank account from taking a sudden hit. Here is how to plan the logistics and handle the payments.
That intro window is a deadline, not free money. If you still have a balance left when the 18 months are up, regular interest kicks in on what is left over.