From Wiktionary, the free dictionary
From Sanskrit साधु (sādhu, “well, proper”).
sādhu
- good, virtuous
sādhu
- sadhu: a holy man, saint, sage, seer.
sādhu
- well
- → Burmese: သာဓု (sadhu.)
- → Shan: သႃႇထူႉ (sàa thṵ̂u)
- → Thai: สาธุ (sǎa-tú)
- → Chinese: 善哉 (shànzāi) (calque)