I have been interested in Thai lakorns for a while now, so I think I have enough experience to recommend several romance dramas.
Torranee Ni Nee Krai Krong - I love the chemistry between the leads! Although this lakorn is a little slow-paced, the leads' other works are fantastic. (Duang Jai Akhanee & Game Rai Game Ruk, etc)
Paragit Ruk Series: Yeut Fah Ha Pigat Ruk - This drama was adorable with a good amount of action, building up suspense, which I personally enjoy. I suggest you also watch the others in the series.
Bpoop Phaeh Sunniwat - Bella Ranee is one of my favorite Thai actresses (Also in Padiwarada and Khun Chai Puttipat) I adore the leads, and it has become one of my favorite lakorns of all time. It's still currently airing, so I feel like there is such a strong focus on the main couple that I hate whenever anyone else gets screen time, especially when their backgrounds haven't been built up from the start. The male lead is the kindest, and it's just heart-warming seeing their interactions. He is very aloof and a bit cold at first, but he plays the character very well.
Favorite line:
FL - "I want to go home."
ML - "I won't let you go." (It sounds possessive without context, but it's actually very sweet)
I can't say how much I recommend this lakorn, and I hope you end up watching it.
* Every drama I mentioned (even the ones in parentheses) are recommended.