That is correct, Jaimie. The foam is intended to block radiated heat by the fact that it consists of a multitude of "cells", similar to the fibre type of insulation. And I would also agree with your comment about water leakage and Thai roofs.
With any form of building insulation it is necessary to examine the "R" value of the product. Some types of foam have a much higher "R" value than fibre insulation, but this advantage can be offset by the cost of installation, and the sealing / water problem mentioned.
The OP has mentioned a "suspended" ceiling, but there my be some confusion over just what he means. Thai methods of building will see gypsum / plaster board ceiling "suspended", and is not a problem to lay fibre type insulation over it. Most of the fibre type available here has an aluminium film on one side of it, which increases it`s "R" value without increasing the thickness of the blanket. What I have done in the past is to install a double layer of thinner material, preferably with one layer laid at right angles to the other.
There is a company in Pattaya that installs the spray type. but they will not come just for one house. That may have changed as it is a couple of years since I last enquired.
With either type it is good practice to have some form of ventilation in the roof space to allow cool night air into it.
May you be in heaven half an hour before the devil know`s you`re dead!