How can I get my parent's permission to go on a trip with my boyfriend (me 19 and my boyfriend 29)?

I'm Vietnamese, my boyfriend is from Singapore. We met online so this September, he will fly to VN and we will have a trip to Da Nang but i don't know how to ask my parents. Pls help !!!
How can I get my parent's permission to go on a trip with my boyfriend (me 19 and my boyfriend 29)?
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