There is only one requirement to get to Bangkok, and that is to get the passport. Personally, we got it from the clerk on our second go, but your mileage may vary. Before entering Bangkok, however, we suggest that you collect some Untraceable Cell Phones. These are essential to the alignment missions in the different chapters of Episode 1, so if you are lacking, you will be wasting time grinding to get them instead of using energy on the missions that require it. We suggest getting between 12 and 50 phones. 12 is enough to complete the missions of Episode 1 to first tier mastery, while 50 will get you all the way through Episode 1 to tier 3 mastery. No other loot items are required.
Chapter 1 is easy and straightforward. Do the jobs. You will have to do the jobs from first to last, as the first job gives money to buy gear for the second, which does the same to give gear for the third. Assuming you do not spend any of your money frivolously, you will hav ejust enough money from mastering each job to move on to the next. Unlike Moscow, the third job in Chapter 1 is mastered easily and quickly without the help of friends.
Chapters 2 and 3 follow the same formula. You must master an alignment job for one of the factions: Yakuza or Triad. Doing so unlocks two more missions, which must then be mastered to move to the next chapter. You can earn some easy alignment points here, as doing a job for one faction or the other gives 3 faction reputation and subtracts 1 from the enemy faction. If you balance it right, your reputation for both factions will stay roughly the same. As mentioned earlier, these alignment jobs require cell phones, so make sure you have some. Chapter 3 also includes a mission that drains your money, so don't go spending it on businesses.
Chapter 4 is the final chapter, and is extraordinarily easy. Master the first job, then finish off the boss. The boss' death will give you experience according to the amount of people you called to help on the job, so call more people in for a huge bonus to experience. After you whack the boss, the Episode resets to let to get tier 2 mastery. Repeat the steps above until you reach tier 3, and voila!