The East India Company might disagree with that.
PMCs can fight and have won, if they're properly utilized and resourced, and especially if there's flexibility about things like rules of engagement and collateral damage.
The Chinese government is not stupid. They have certainly learned a few invaluable lessons observing America's recent misadventures with nation building.
Violent coercion might sound immoral, but is nothing unusual in statecraft. However, for it to be effective, it has to be carefully calibrated. You probably wouldn't want to push Thailand closer towards what you'd call her johns.
If you really, absolutely want to and just have to go there, a carrot or stick approach will be more optimal, if not an imperative.
Those elections in what is or was Eastern Ukraine weren't necessarily bogus. The locals who stayed and voted tended to consider themselves both Ukrainian and Russian or just Russian. Those who didn't tended to have fled, though that obviously wasn't an option for everyone.
Moreover, if fraudulent elections are necessary, you may want to reconsider your invasion plans. It might seem easy to invade and proclaim victory (just ask George W Bush circa 2003), but it isn't always easy to occupy, nevermind govern and develop a country, especially a place as fractured as Burma.
Ultimately, if you have to rule, nevermind assimilate tens of millions of foreigners, it will be ideal to be both feared and loved. Your subjects need to appreciate your rule and prefer it over the alternative, assuming an alternative is even plausible.