the SDK plugin does not support SAMP, in order to send a message to the chat you will have to write the code manually, as here:
#define SAMP_CHAT_INFO_OFFSET 0x21A0E4
#define SAMP_FUNC_DEBUGLOG 0x64520
typedef int (__cdecl *__DebugLog)(void *g_Chat, char *log, ...);
__DebugLog...