If you're leaving your money in Thailand and want to invest it in Thailand, but are also lookin for a low risk investment, then you might consider the property purchase & then rental route that someone else suggested. Someone suggested buying a condo and looking for a rental income - possibly of more interest might be buying or building a few "hongtel" type rooms near where you live and renting the rooms out to Thais.
Your personal situation will be relevant - living in the city or countryside, married or not? In the countryside it's cheaper & easer to buy a small plot of land near a school or local factory and build a hongtel. With a Thai wife she can probably also help with stuff like finding a good plot to build on and getting you a good price for it. In the city it would be more expensive to do and maybe not as easy to find the land. (If you're single and land owning is an issue for you as a foreigner, you might consider setting up a Thai company to buy the land and then you could rent the land from that company on a long lease for a pittance).
Anyway if you build a small hongtel you could easily have 10 - 15 rooms for rental to Thais. They might bring in an income of THB1,000 per month per room. Plus you have the property to protect your capital. Maybe an outlay of about THB10,000,000 to build 10 - 15 rooms & buy the land.
Very occasionally you come across a ready made hong-tel property up for sale - maybe that's something also to consider if the price is right.
