Formal:
* ราตรีสวัสดิ์ ที่รัก (raatri sa-wat dii thi rak) - This is a very formal and polite way to say goodnight. It literally translates to "good night, my love."
Informal:
* ฝันดี ที่รัก (fan dii thi rak) - This is a more casual and affectionate way to say goodnight. It literally translates to "sweet dreams, my love."
* นอนหลับฝันดีนะ ที่รัก (non lab fan dii na thi rak) - This is a very sweet and endearing way to say goodnight. It literally translates to "sleep well and have sweet dreams, my love."
Romantic:
* ราตรีสวัสดิ์ คนรัก (raatri sa-wat dii kon rak) - This is a romantic way to say goodnight. It literally translates to "good night, my love."
* ฝันดี คนรัก (fan dii kon rak) - This is a romantic and casual way to say goodnight. It literally translates to "sweet dreams, my love."
You can also add a personal touch by adding the person's name or nickname after "ที่รัก" (thi rak) or "คนรัก" (kon rak).
For example:
* ฝันดีนะ ที่รัก (fan dii na thi rak) - This translates to "sweet dreams, my love."
* ฝันดีนะ คนรัก (fan dii na kon rak) - This translates to "sweet dreams, my love."
Ultimately, the best way to say "goodnight my love" in Thai depends on your relationship with the person and the context of the situation.