I get the same in Bangkok, the signal quite often drops to 4G or 4G+ using 12Call. 5G chews through the juice so I'm in the habit of turning power saver on. Sammy S22+. great phone but sucky battery life.
also 5G is pointless if the server ain't feeding you the data all that quickly. Google Play Store I'm looking at you. their CDN must be in Ulan Bator because often it's better to connect to a VPN if you have a large number of updates.