The Thai YWCFTS remake is trending (?) on Weibo right now. Here's a Chinese article on the casting:
http://star.ettoday.net/news/943526
Translation (CN to EN)
Thailand has been actively adapting classic Asian dramas in recent years, including the likes of
Full House,
Princess Hours,
It Started with a Kiss as well as
Fated to Love You. On the 12th, reports have confirmed that an adaptation of
You Who Came from the Stars which starred Kim Soo-hyun and Jeon Ji-hyun is in the works. Do Min-joon will be played by uber-popular actor Nadech, and Matt Peeranee has been cast in the role of Cheon Song-yi.
(Introduction of Nadech) According to an article from Dara Daily, the producer of the drama stated that, "we chose him as our male lead when we first purchased the rights to the remake."
(Briefly talks about casting rumours for Cheon Song-yi, as well as a short introduction of Matt)
The production company also revealed that Park Eun-ji, the script writer for the Korean version of YWCFTS, wanted the Thai side to pick a superstar to play the role of the male lead. "She also asked about the potential options for the female lead because she was very concerned. We hadn't found our person then, but now we are set on Matt Peeranee."
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Contrary to reports, I think the Korean side did not explicitly ask for Nadech. They requested for a superstar and the first person who came to mind for the Thai side was him. And this is pretty much solid confirmation for the main cast if the quotes are accurately translated.