How to create a row number with specific order in postgreSQL

Can anyone tell me how to get a row number like in the table below?

I have data:

• IDR (1 Month - 12 Month)

• USD (1 Month - 12 Month)

• SGD (1 Month - 12 Month)

• AUD (1 Month - 12 Month)

I want to have a row number exactly like the column "NO", where IDR goes first, then USD, SGD and AUD.

I tried using order by Currency, left(month,2), but IDR doesn't go first.

Add a computed column to the query that uses a window function with an appropriate ORDER BY clause:

SELECT row_number()
          OVER (ORDER BY CASE WHEN currency = 'IDR' THEN 1
                              WHEN currency = 'USD' THEN 2
                              WHEN currency = 'SGD' THEN 3
                              WHEN currency = 'AUD' THEN 4
                         END,
                         split_part(month, ' ', 1)::integer),
       ...
FROM ...