Controlling a motorcycle with a heavy load is not so easy, and traffic in those parts of the world is actually quite wild, most people do take some time to get used to it. Having to learn both simultaneously would be a very tough task, with very real risks involved - for you, your passenger, and possibly others as well. If it was me, I would not deliberately put myself into that position.

When doing a self-drive/ride tour in Asia, traffic is probably one thing that´s just as likely to get you into trouble as other security issues, or some exotic diseases, so it shouldnt be underestimated. It´s also good to keep in mind, that as a falang, you´re considered the one with the thicker wallet, so pretty much anything that might happen - you pay.

Don´t get me wrong, I do not mean to put you off at all, these are truly wonderful countries to travel; beautiful, exciting, warm, friendly and cheap - and doing them on 2 wheels is even more fantastic. Some of the best riding I´ve ever done in my life has definitely happened in this region, and usually people have no problems. But considering all this, I would find a way to get some experience of riding a bike before I´d set off. And preferably also go riding in Asia 1-up first, before doing it 2-up.

(Here´s just a thought, even though this may not be your solution for 2-up:
a group of my friends, who usually spend their winters in Thailand, all now ride 115 or 135cc Yamaha Nouvo scooters (automatic), and they all have decades of riding experience; all of them also have big bikes back home, some also in Thailand, but they seem to be quite happy with these small "chicken chasers"... (it does look funny, when big falangs are riding such small bikes, though!!) I joined them 3 years ago, when they tried to enter Vietnam with Nouvos (wasnt allowed, but we had a great time in Cambodia & Laos!)... and since then, they´ve tried to enter Burma, and toured extensively in many parts of Thailand with them as well. Next January, they´re planning a ride to Malaysia&Indonesia! This kind of vehicle is surprisingly bulletproof, and wheels&tyres can be fixed in even the smallest villages in the backroads. The locals ride them year-round, even in the muddy roads in the rainy season, and they often have luggage like you would not believe, so a good rider can take them surprisingly far. It´ll run at 100-110kms per hour all day, uses almost no gas, and I believe nowadays costs around 1000-1300 euros new. Some of those Nouvos now have over 20.000kms on the clock, and they´ve never missed a beat. Being light, and having no clutch and gears it´s also much easier for a beginner to learn. I didn´t understand their enthusiasm for these scooters at first, but as I´ve now done some 6-7 thousand kms with them, there´s no denying it is a very economical and surprisingly capable "bike" to tour SE Asia)