From a careful goe-strategic analysis, I would suggest Russia backs down from such a plan, Southeast Asia is too far away and the physical body in the form of water that separates Russia from SE Asia would make such an adventure ludicrously expensive. IMO, the next expansion after Ukraine should be (as Tatarigami from X suggests) the Baltics, if the situation permits. Once the Baltics are in hand, that means either:
- NATO is dead
- The U.S. cease to be a superpower that is capable of projecting power and stop Russia
From there Russia should use the manpower from acquired land to adventure North, towards Finland. Finland might not have that many population, but what they have is a huge real estate in the form of land (est 338,472 sq km) and coastline (31,119 km (19,336 mi
)) That would guarantee security to Saint Petersburg and the ability of the Baltic fleet to sortie towards the Baltics unopposed by the Gulf of Finland.
A successful absorption of Finland technically means that Russia is a stone's throw away from securing Norway's long coastline and removing the threat towards the Russian navy's base in Murmansk (HQ of the Northern fleet).
Absorption of Norway into Russia's private property meant that the Russian long-range bomber group would have absolute free reign in the GIUK gap and flying from newly acquired bases in Bodo and Orland threatens shipping in this increasingly crucial shipping line.
So it's going to be Baltics >>> Finland >>> Norway. In the first phase
For the Next phase, it's up to Russia. They could absorb Sweden and turn an estimated 3,218 km of coastline into the previously added coastline from neighboring Baltic states and Finland and turn the Baltics into a Russian lake or turn the gun towards Poland.
This is in my opinion, a more sound strategic goals for Russia and put into account Russia's unique security concerns