I would suggest using a cement board aka durrock. The tile will adhere to it much better. Some of the tile guys/gals on here might know of a better product as I know they are constantly coming out with new stuff.
You can not tile directly over a single layer of plywood (subfloor), you would need to add an underlayment of at least 3/8" ply or thicker. That is IF the framing was built sturdy enough. Can you tells us how this platform is constructed and with what?
If the framing meets standards you're better off installing a tile backer board or a membrane such as Ditra if you're able to buy just a small amount.
TILE GUY - retired- TROY, MI - Consulting by phone/internet - PAYPAL
DITRA Installs - KERDI Watertight-Mold-Free Showers. I have NEVER made a mistake, I thought I did ONCE, but, I was WRONG!A+ BBB rating - est. 1987 - over 50 yrs. exp.