How do identify if one company is a MNC or SME company?

If you are referring to Singapore context, there are mainly 2 variables:

1) Annual Sales Turnover

2) Employee Size

SMEs are now defined as companies with:

(i)
at least 30% local shareholding; AND (ii)
Group annual sales turnover of not more than $100 million OR Group employment size of not more than 200 employees.