Answer by msp9011 for sed/awk/python replace all spaces between characters after string match

Using sed:

sed -e 's/ //3g' file

exmpl 0 thisarethespacestodelete
exmpl 1 morespacestodel
exmpl 2 orsmthcompletelydifferent
exmpl 12 yetanotherline

will do replacement from the 3rd match