Haven't you been on a multi-vitamin for some time now though? It will have thiamine in it, so I don't think it would apply in this case. Just my opinion.
Multivitamins have minimal amounts of most nutrients in ratios that may or may not be right for the patient taking them. It is an erroneous assumption to think that they would be sufficient for any sick patient, especially someone ill with ME/CFS.
There are numerous reports of people adding thiamine to their regimen and it being a real game-changer for them.
has 12.5 mg in the ortho multi men I take.
That's a pretty low dose. I'm taking 750 mg of Benfotiamine or else I test low in thiamine.
Noticed more sustained energy as a effect from thiamine. I wonder if maybe that's why I feel the same? Could be the veggies but I have long sustained energy. Today I was working as fast as I could for 5 hours straight.
This describes what thiamine does, including reducing fatigue:
https://selfhacked.com/blog/thiamine/
He did mention high oxalates but I eliminated basically all of it and felt no difference.
Exactly how did you do that and for how long? Reducing them in your diet is one thing, but that just stops them from adding to the deposits you already have. Typically, if you have an oxalate problem You will have oxalates deposited in places throughout your body, including your eyes, heart, kidneys, joints, mitochondria, and everywhere else. It typically takes a long-term effort, including taking potassium, magnesium, or calcium citrate prior to each meal, a good deal of vitamin B6 in the form of P5P, and a low oxalate diet, for 1 to 7 years. The idea is to reduce them being deposited, and then to lower the gradient so that they start to come out of where they are stored. Oxalates can cause all kinds of mischief while you have them. They are a toxin, but they do not use the normal detox pathways, this is how you have to detoxify from them.
Although I unfortunately started smoking cigs again.
This is more than unfortunate. It is directly damaging to your body, and put stress on your ability to detoxify, which sounds like it is already stressed. This would greatly increase your need for detoxifying nutrients.