[Jackson]

'Noi' is very similar in meaning to other Thai words/nicknames such as 'Nit', 'Lek', 'Jiap' and 'Jip' etc... All of this names mean literally small or little etc..

Perhaps when they were born/young or whenever, they were little or small in body-size, spoke a little or ate a little or smiled a littled etc...

So yes, 'Noi' has meaning however to find out exactly why she is called 'Noi' you will have to ask her family.