Taekwondo would be good because it stresses leg strength, flexibility, balance, hip strength, and core strength. All very useful stuff. Your previous experience with kicking will also be a good asset.

Why not finish your training in TKD?

I'm getting into Muay Thai, kinda like kick boxing in Taiwan. I've taken two years of Tar Kwan Doe before this, and remember it all very well. So I was wondering if having a background in another martial art, tae kwan doe in particular, would help?