Where was the best place you visited in Thailand and why?

Myself and partner alongside brother and his partner are travelling to Thailand arriving 13th April. Brothers first time there. My partner and I have already been in 2024 and travelled to Bangkok, Pattaya and Phuket, we also did a little island hop whilst there (only had 17 days). This time we are doing 3 weeks and I wanted to seek some advice from others. Our favourite place was Phuket as we loved the beaches and rented mopeds. We cut our Pattaya trip short and moved on as it wasn’t for us. We did no research last time and just went where the wind took us. Discussed Koh Samui but nothing set in stone. 🙂