Have you tried writing a food diary, noting the carbs in everything you eat and drink each day? This can be helpful in showing you your true carb intake (we often miss out quite a bit if we are asked to estimate afterwards), plus it may highlight areas where you can reduce carbs by using an alternative. I'm not familiar with what sort of foods might be available to you there, so can't really comment - my only experience of Vietnamese food was in a restaurant in Paris in 1981! 🙂
34 units of novorapid doesn't sound particularly high to me, and of course it can vary widely from person to person. I do find it very true though, that the greater the carb content of a meal, and therefore the greater the dose of insulin, the more likely I am to get unpredictable levels. I'm currently training for a half-marathon, so my doses are quite low - around 15 novorapid a day - but a few weeks ago they were pushing 40 units a day. I consume around 100-150 grams of carbs a day.
I've heard other teachers employing a similar strategy regarding levels before lessons - certainly testing beforehand, plus getting more predictable control overall should give you more confidence that you are not going to drop low. You should certainly be able to achieve a situation where hypos become a rarity without having to maintain your levels too high.