I'm in HCMC now. The apps (Grindr, Blued, Jack'd - I dont use Hornet) are very busy. Several guys will solicit massage + fun to you; come to your room for 500k VND and up. But if a guy is prepared to lower the rate to 500k VND you have to be a bit careful - or dont mind if he is short, a bit chubby, small cock or with a face that certainly not look like the (blured) pic he sent to you earlier! Premium guys (stunning/lean gym guys, tall and with big cock) charge 1,000k-1,500k VND/hour - asking price is higher but rates are certainly negotiable. Don't expect much for the massage part - that is not why they come to your room. It you msg a profile in Grindr with stunning lean or muscle body/torso and no face, and if you get a reply, it will most likely be a MB and soon the issue of money will turn up when you chat with him. Some will even clearly state in the profile that they offer massage; then you just ask for some pics and negotiate the price - works very easy. Craigslist is also easy way to find MB here.
Finding non-commercial gay lads for (free) sex is not that difficult when using the apps (I'm tall <45y with a decent body (but by no means slim anymore) and I get a lot of messages in the apps which lead to/could have lead to encounters if I had the time/interest, but again the guys can be short, <30y or on the chubby side or with a less attractive face; so you need to be selective. Most speaks limited English. I find it easier to hook up with guys here than in BKK.
1 USD= 22,700 VND as I write this.