Please try this. You can add other subqueries for other services this way:
Select Top 1000000 tblAssets.AssetID,
tblAssets.AssetName,
tblAssets.Domain,
SNMPService.[SNMP Service Started]
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Left Join (Select Top 1000000 tblServices.AssetID,
tblServices.Started As [SNMP Service Started]
From tblServices
Inner Join tblServicesUni On tblServices.ServiceuniqueID =
tblServicesUni.ServiceuniqueID
Where tblServicesUni.Name = 'SNMP') SNMPService On tblAssets.AssetID =
SNMPService.AssetID
Inner Join tblComputersystem On tblAssets.AssetID = tblComputersystem.AssetID
Where tblAssetCustom.State = 1 And tblComputersystem.Domainrole > 1
Order By tblAssets.AssetName