In my local language (Bahasa Indonesia) there are no verb-2 or past tense form as time tracker. So, I often forget to use the past form of verb when speaking english.
I saw him last night (correct)
I see him last night (incorrect)
But i think both has the same meaning and are understandable,
No, ‘I see him last night’ is always incorrect and will be only just barely understandable. It is a very serious and basic error, and it will be tiring for a native speaker to converse with someone who speaks like this, because they will constantly have to be remembering what the person really means. It will not be ‘immediately obvious without thinking about it’.
Someone just asked this question recently, and I replied, saying that ‘I see him last night’ is never correct. That is exactly what i meant.
There is a certain poetic sense in which “I see” works. “I see him last night in my dreams” although not technically correct. However, generally speaking “I saw” is the right usage for past events. Much prose writing in English novels is in the present tense although they are about past events. The author superimposes himself however on the situation as if it were the present.
You are correct that both are understandable.
The only other possible everyday meaning I could think of would be ‘I see him [in my mind’s eye] last night’; that is, I am, at this very moment, imagining him last night. But it should almost always be clear from context which one is intended.
‘Correct’ doesn’t mean ‘understandable’, though. If I say ‘Me want have fooding’ it’s pretty clear what to understand from that, but it’s not anywhere near correct Standard English grammar. If you lived somewhere where you spoke a dialect of English in which this was acceptable grammar, however, then it would be correct for that dialect.
Yes, I understand it. I hear a lot of this incorrect grammar from my wife. I would expect that the person that spoke this was possibly Chinese. In Chinese there are no tenses or plurals. No he or she pronouns. The context tells all. So it might have been a direct translation from Chinese.