If a host serves you dinner or if someone treats you to meal, you should use this phrase at the end of the meal to express gratitude.  Note that at the beginning of a meal, you would say "itadakimasu" instead. Pronounce this phrase as goh-chee-sou sah-mah deh-shee-tah. " It essentially means something along the lines of "thank you for your hard work.""  The implication is that the listener has worked hard and deserves to rest. The phrase is polite and shows gratitude for that person's hard work. Pronounce this saying as oh-tsoo-kah-reh-sah-mah desu. " This is not standard Japanese. Instead, this form of saying "thank you" is only found in areas near/aroun Osaka.   Ookini can mean "thank you."It can be used at the end of a sentence to smooth relations, or it can be used on its own to show appreciation to someone close. The term was originally a way of indicating quantity and was used with arigatou as ookini arigatou. Over time; however, the phrase was shortened to ookini.  Pronounce ookini as oh-kee-nee.  In non-romanized format, write it out as おおきに.

How would you rephrase that briefly using Vietnamese?
Sử dụng "gochisou sama deshita" sau bữa ăn. Khi hết giờ làm việc, hãy nói "o-tsukaresama deshita. Ở Osaka, nãy nói "ookini.