It would depend on the contents of the "lacquer thinner". Some people call mineral spirits "paint thinner" and/or "lacquer thinner". Some lacquer thinners have acetone, ethyl acetate, toluene and other components in it. Those aren't good for the paint job on a bike but they aren't particularly toxic either. Methanol may also be present and that is more toxic.

Some of the compounds can actually be formed in your body. Acetone can be present in urine. It's not good to have it in your urine because it's a signal of things wrong with you but it can be there. If you drink isopropyl alcohol, it metabolizes to acetone. Ethyl acetate is an ester and we use esters everywhere in our food. Artificial flavors can be and are esters. The "banana" odor of Triflow is from isoamyl acetate and is the flavoring for artificial banana flavor.

Again, don't drink it, use it in a well ventilated area and wear gloves.