Just because he is your boyfriend already doesn't mean you should stop flirting. Flirting keeps a relationship light and healthy--plus it will show him that you’re still very into him. Play coy and tease him (but not too much.) You could even tease him about not kissing you (which is a pretty direct way of saying ‘I want you to kiss me!’) Send him flirty text messages when you guys aren't together. Flirtatious, funny texts are a great way to be cute with him even when you’re not around him. Just keep in mind that you don’t want to overload him with texts--that can be a turn off. Guys like to feel like they are the big, strong men in girls’ lives--so make your guy feel that way. Even if you don’t necessarily need him to open a tightly-lidded jar, it's a nice confidence boost for him when you say something like ‘ooh! Look at those muscles!’ This is, of course, another form of flirting, but it is the kind that will boost his confidence--hopefully giving him the confidence to then lean in and kiss you! Being direct has its ups and downs. The ups are, you will most likely get results immediately, and it will show your guy how confident you are--which is very sexy. The downside is that the results you get immediately might not be the ones you want. He may still need some time to overcome his shyness, or he might not be as into it as you thought. No matter what, you will get results--and you are taking the pressure off him by telling him exactly what you want. You can make your request sexy and still direct. When you are hugging goodbye, lean in close so that your lips brush his ear and whisper something like “Kiss me” or “I want to kiss you.” Chances are, your words, and that little brush of your lips, will be enough to make him lose any shyness he might have and go right in for the kiss.

How would you rephrase that briefly using Vietnamese?
Tán tỉnh bằng ngôn từ. Khiến anh ấy cảm thấy tự tin. Thẳng thắn nói rằng bạn muốn anh ấy hôn.