我想给他写一封感谢信:
I want to write him a thank you letter.
英语里 感谢信 通常翻译为 thank you letter.
自己的翻译的,希望对你有帮助—— ♥
I want to write to him expressing my thanks.
2.I want to pen a letter of thanks to him.
I want to write a letter of thanks to him
I would like to write him a letter of thanks