Maybe:
RunCommandIndir('I:\170724190300_ffplay_euronews\bin',I:\170724190300_ffplay_euronews\bin\ffplay.exe,['-i ', 'http://euronews-ru-p9-cdn.hexaglobe.net/b0cdf3de7985b6e1e0a829499e4bdbae/5977a4f4/euronews/euronews-euronews-website-web-responsive-2/ewnsabrrupri_rus.smil/ewnsabrrupri_rus_540p.m3u8'], outputstring_ );
(just separate the parameters with a comma, don't join them yourselve)
Sorry, cannot test myself, don't have a Windows computer currently.
Bart