In India, 100 thousand is sometime referred to as 1 lakh, while sometime as 1 lac. I am not sure if lakh is correct. Sometimes, I find the people writing more than one lac (or lakh) as lacs (or lacs). For example: The seller has received a sum of Rupees three lacs seventy-six thousands five hundreds thirty-six. I am not sure if lac, thousand and hundred were correctly converted as lacs, thousands and hundreds, in the instant example. Can anybody shed some light?
As WS2 has pointed out correctly, lakh is part of Indian English. Therefore, the cited example must read
The seller has received a sum of Rupees three lakh seventy-six thousand five hundred and thirty-six
When quoting sum (or any currency values) in written words, pluralization of units(thousands , hundreds) is not acceptable since we are expressing the numerals as is in written form (We know the exact value).
Thousands, lakhs cab be used in generic sentences. For example,
Thousands of people were affected in the recent Chennai floods.
Lakhs of devotees visit Tirupati everyday